Capillary column gas chromatography using radiolabelled compounds is an important tool in analytical chemistry, but its performance, especially with low energy beta particles, is limited by the radiation detectors which are currently used. We propose to develop a system based on solid state sensors which will provide extremely high sensitivity without compromising resolution. We will accomplish this using avalanche photodiodes (APDs), which have demonstrated the ability to detect low energy beta particles, including those from tritium, with high efficiency. An APD is a superior sensor for such radiation because it can be made with a very thin front window and has internal gain to provide a very high signal-to-noise ratio. Moreover, APDs are compact, allowing good resolution in capillary column gas chromatography and can be made in arrays, allowing very high sensitivity for small samples. The research in Phase I was completed successfully and all of the technical goals were met. Phase I demonstrated that APDs could be fabricated with efficiencies exceeding those of any other solid state detector. In Phase II, the research will be continued and expanded to include the fabrication of complete detector systems suitable for incorporation into gas chromatography instruments.